Compared with civilian (home) speakers, public broadcasting is also counted as a kind of professional audio. However, the professional audio that everyone generally refers to refers to the performance stage (performance) speakers, and public broadcasting is different from this kind of speakers.
Very simple public address system and features
Public broadcasting is a broadcasting that serves the public in a special category. In the basic situation, the public broadcast data signal is transmitted according to the broadcast route arranged in the broadcast service project area, and is generally a unilateral (outgoing) cable television broadcast.
Public broadcasting is generally set up in administrative agencies, military, companies, colleges, communities, commercial buildings, shopping malls and various exhibition halls to send news and internal information content, announce work and rest time data signals, show music background and It is used for communication systems (Paging-such as broadcasting to find relatives) and forcibly inserting emergency broadcasting of extreme weather safety accidents.
The public address system is also effective for wireless data transmission, but it is not popular.
A public address system must be equipped with at least the following stages: broadcasting speakers, broadcasting power amplifiers, and microphones.
The low output power broadcast power amplifier below 100W is generally a spare external stage, and it is not necessary to be equipped with a pre-amplifier, alias combined broadcaster. Broadcast power amplifiers with large output power (for example, more than hundreds of watts) generally require additional broadcast preamplifiers. However, whether it is the preamplifier of the integrated broadcast body or the separate broadcast preamplifier of the company, the key entry needs to be arranged with priority. Generally, there is at least one microphone at the top priority. The data signal of this microphone can automatically suppress other key-in data signals (that is, it has a full-automatic "silence" function), which is convenient for communication systems and emergency safety incidents. The emergency broadcast can be inserted forcibly. This is also different from the general HiFi (or technical professional) preamplifier and its mixer.
The professional terms in the system software: microphone, route, power amplifier, speaker, etc. are all known to the general electro-acoustic equipment staff or enthusiasts of electro-acoustic equipment speakers. However, the broadcasting route, broadcasting power amplifier and broadcasting speakers are slightly different from ordinary speaker cables, power amplifiers, and speakers.
*The use of cables is not the same
The most notable difference is that the broadcast route is generally very long (500 meters or even more than a kilometer), while the speaker cable of general professional audio equipment rarely exceeds 100 meters. In order to reduce transmission loss, broadcast data signals are normally transmitted using a "high voltage/low current" method. Therefore, the broadcast route generally does not need to use expensive speaker cables but only the general Category 5 twisted pair; if it is equipped outdoors, it needs to add lightning protection equipment.
*The output mode is different, let's talk about uniform power amplifier and constant resistance power amplifier.
Because the system software uses high-voltage transmission, the broadcast power amplifier must show high-voltage data signals. Generally, broadcast power amplifiers have built-in output transformers to increase (or standard) their output voltage, which are called "uniform" power amplifiers. The output terminal of the uniform power amplifier is marked with 70V/100V/120V/200V and other allowable output voltage (NormalOutputVoltage) specifications and models, instead of the rated value characteristic impedance marked value (European mother) like the technical professional power amplifier, the latter is also Therefore it is called "constant resistance" power amplifier.